The invention pertains to a method for measuring the temperature in a mold by means of a fiber-optic measuring method and to a correspondingly designed mold. For this purpose, light waveguides, through which laser light is conducted, are provided on the outside surface of a mold. The invention serves to improve the local resolution of the temperature detection in a mold in comparison with the known temperature detection systems and makes it possible in particular to improve the detection of longitudinal cracks and fractures.